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Spectroscopy of Alpha Decay
Alpha decay spectroscopy involves experimental determination of the energy and activation of an unknown alpha decay source using a calibrated spectroscopy system. Following the determination of the source's activity and emission energy levels, the range of alpha particles in air will be determined. Alpha particles are doubly ionized helium atoms, and are ejected with very high energy from the nuclei of some radioactive isotopes. The alpha decay process occurs most often in isotopes with an atomic number greater than 82. It occurs spontaneously in these sources because it is naturally favored as a process that releases high amount of energy as well as ridding the isotope of a large mass.
The experimental apparatus used in this lab consists mainly of an alpha emission source, a vacuum pump, a detector, and a computer to interpret the data gathered. The first experiment conducted is done to measure the alpha spectrums of the Cm-244 and Pu-239 sources used in the apparatus. Alpha particle energy is typically within the range of 5-8MeV, but can be as high as 10 MeV. Activity levels of the sources are then calculated based upon calibration data of the apparatus and the emission spectrum graphed onto the computer. The observed emission spectrums and peaks are unique to individual isotopes, and can be used to identify alpha sources. The second experiment in this lab concerns the range of alpha particles in air. An alpha particle source is positioned at known distances away from a detector, and alpha counts are made at each distance. Using the data collected, a theoretical calculation of count rate vs. distance between the source and detector is made. A sample graph is shown below of transmission efficiency vs. distance.
The first important application of alpha spectroscopy is identifying an alpha source. The emission spectrum of a source is unique to that isotope, and thus can be compared to known emission spectrums and used to identify a source as being a certain element and isotope. |
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NEEP Lab Course Instructor:
Yaron Danon, vist Dr.
Danon's web site |
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